1. Field of the Invention
The invention relates to ultraviolet, visible and infrared absorption, and more specifically, to the use of a particular class of ultraviolet, visible and infrared absorbing pigments. It also relates to protective eyeware.
2. Description of the Prior Art
In recent years increasing attention has been given to the importance of protecting the eyes and skin from radiation emitted by artificial and natural light sources. Prolonged exposure of the eyes to reflected solar ultraviolet radiation is believed to result, for example, in the formation of cataracts and general tissue damage.
A variety of commercial optical filters have evolved to meet the threats posed by these radiation environments. Such optical absorption systems include sunglasses, aircraft and automobile windows, welders glasses and others.
In the case of sunglasses, two general types of materials are currently employed as practical absorbing components. Metallic films deposited onto plastic lens substrates are very effective sunscreens providing broadband attenuation of electromagnetic waves from the ultraviolet into the near infrared region of wavelengths. However two disadvantages are associated with this type of sunglass system. Manufacturing steps beyond the formation of the basic plastic lens are required and secondly, waves incident from the rear and reflected directly into the eye pose a new problem and require further manufacturing modifications.
Dyes and pigments comprise the second general class of optical absorbers. These molecular or polymeric elements are either deposited as thin films or are dispersed into the plastic matrix. Disadvantages of this type of system are often the inability of the dye or pigment to absorb radiation sufficiently over all the ultraviolet wavelengths and a tendency to photodegrade. Photodegradation is particularly common to organic dyes and pigments.
The use of melanin, an easily synthesized biopolymer, as a sunglass pigment, offers several advantages over the prior art. This advantages will become evident in the following pages.
Prior art does exist for melanin as a sunscreen; however, this prior art is restricted to the use of melanin as an ultraviolet protecting pigment in a cosmetic cream applied to the skin (see Japanese Patent-kokai-74 71, 149).